This invention relates to a safety shutoff valve. It relates more particularly to a valve for stopping the delivery of liquid fuel to a fuel tank or a fuel truck when the same are filled to the desired level.
The subject valve has special utility in connection with the refilling of large fuel trucks at a tank farm, under both high and low fuel delivery pressures, and the invention will be described specifically in this context.
Various devices have been proposed for shutting off the flow of fuel into a fuel storage tank when a predetermined liquid level is reached in the tank. One type is shown in U.S. Pat. Nos. 2,464,456 and 2,569,110. This type of valve employs a float which is connected to a valve member. When the liquid level in the tank reaches predetermined height, the float rises and closes the valve member which stops the flow of fuel into the tank. Provision is also made for bleeding fuel from the fill pipe leading to the valve to relieve the pressure in that line prior to uncoupling the pipe from the valve.
While that type of shutoff valve works satisfactorily at relatively low fill pressures, it does not respond quickly enough when the fuel is being injected through the valve into the tank at higher pressures, on the order of 90 psi. Sometimes the valve float does not have time to respond to the rapidly changing liquid level, with the result that the valve does not shut off until after the tank is filled to the brim. This leaves no room to bleed off the fuel remaining in the fill pipe. Consequently, when the pipe is uncoupled from the valve, fuel spurts from the end of the pipe over the tank and onto the ground.
Further, fuel shutoff valves of this type should be more rugged so as to handle the higher fill pressures used today. Specifically, the shutoff and bleed mechanisms must be able to withstand the large forces developed when the valve member is slammed against its seat by the incoming high pressure liquid.
Also, the prior valves include no provision for automatically shutting off the control valve located between the storage tank and the fill pipe. Consequently, if the operator forgets to do this, when be uncouples the fill pipe from the subject inlet valve on the truck, fuel will flow out of the pipe onto the ground until the operator has the presence of mind to shut off that valve located at the storage tank.
As a result of the foregoing, fuel shutoff valves of the above type have not been as widely used as they might be in connection with the high pressure filling of fuel tanks and fuel trucks.